A Phylogenetically Based Infrageneric Classification of the Parasitic Plant Genus Cuscuta (Dodders, Convolvulaceae)

Abstract—

Cuscuta (dodders, Convolvulaceae) is one of the largest and most economically important lineages of parasitic plants. The genus has a sub-cosmopolitan distribution with more than 75% of the species diversifying in the New World. The last monograph, published by Truman George Yuncker in 1932, provided a solid species-level taxonomic foundation. However, as revealed by recent phylogenetic studies, its infrageneric classification has been in great need of a taxonomic reappraisal, mainly because the morphological characters used in the previous classifications have been greatly affected by convergent evolution. Several recent phylogenetic and character evolution studies with broad sampling, as well as species-level revisions, have illustrated the deficiencies of previous classifications and provided an explicit and robust phylogenetic framework. Here we propose a new phylogenetic classification that places all 194 currently accepted species of Cuscuta into four subgenera and 18 sections. Sections have a strong morphological and biogeographical predictive value and include from one to 31 species. Thirteen section names are new or applied for the first time at the sectional rank: Babylonicae (Yunck.) M. A. García, Subulatae (Engelm.) Costea & Stefanović, Obtusilobae (Engelm.) Costea & Stefanović, Prismaticae (Yunck.) Costea & Stefanović, Ceratophorae (Yunck.) Costea & Stefanović, Umbellatae (Yunck.) Costea & Stefanović, Gracillimae Costea & Stefanović, Californicae (Yunck.) Costea & Stefanović, Indecorae (Yunck.) Costea & Stefanović, Oxycarpae (Engelm. ex Yunck.) Costea & Stefanović, Racemosae (Yunck.) Costea & Stefanović, Partitae Costea & Stefanović, and Denticulatae (Yunck.) Costea & Stefanović. An identification key to sections is included together with an overview of morphology, geographical distribution, taxonomic notes, and lists of included species.